Drillable drill bit nozzle

ABSTRACT

A drill bit nozzle providing a through bore for the passage of drilling fluid through a drill bit. The nozzle is made of a material or materials which can be drilled through by standard well bore drilling equipment. The material(s) are selected to provide a surface to the through bore which has a relatively high resistance to erosion to withstand the abrasive and corrosive impact of jetted drilling fluid. Embodiments are described using a hard chrome/copper combination and a single rubber material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of International Application No.PCT/GB01/01506, filed Apr. 2, 2001, and published under PCT Article21(2) in English, and claims priority of Great Britain Application No.0008988.8, filed on Apr. 13, 2000. The aforementioned applications areherein incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to drill bits and nozzles used inconjunction with drill bits for use in the drilling of oil well bores orother earth drilling applications.

2. Description of the Related Art

Rotary drill bits are well known in the art and typically comprise adrill bit body upon which are mounted cutting elements made of a hardmaterial such as tungsten carbide or diamond. The drill bit bodies aretypically provided with nozzle passages for circulating drilling fluidfrom the interior of the drill bit toward the point where the cuttingelements engage the bottom of the bore hole.

Nozzles, both of removable and fixed construction, may optionally beattached to the lower side of a drill bit body and at the end of thenozzle passages for facilitating the jetting of drilling fluid throughthe passages at the bottom of the hole, thereby providing both alubrication function in addition to assisting in the carrying away ofloose debris and other cut material.

It is recognised in the art that the drilling fluid is very abrasive asit jets through the nozzles and accordingly hard materials have beenemployed in the past for constructing drill bit nozzles. Such materialshave been required to withstand high drilling fluid jet velocities andhigh pressure differentials across the nozzles.

In our co-pending British Patent Application Number GB9930287.9 there isdescribed a drill bit body which is made substantially of a materialthat may be drilled through by standard or conventional earth boredrilling equipment. Such technologies may be beneficial when, forexample, it is desired to drill with casing and it is desired to leavethe drill bit in the bore hole during the cementing of a first sectionof casing. After the cementing has been complete, a further and smallerdiameter drill bit may be employed to extend the well bore and to dothis the subsequent drill bit is required to drill through the firstdrill bit employed.

However, this technology has not been possible until now if the first orearlier drill bit comprised nozzles as nozzles, previously, haverequired to be made of a hard material for reasons described above thatwould resist any subsequent attempt to drill through the nozzles.

It is an object therefore of the present invention to provide drill bitnozzles that are constructed to withstand the abrasive and erosiveimpact of jetted drilling fluid, while also being suitable forsubsequent drilling operations intended to drill through drill bitbodies to which the nozzles are attached, and indeed the nozzlesthemselves.

A further object of the present invention is to provide a method ofdrilling a well bore, wherein the drilling method is that commonly knownas drilling with casing and wherein subsequent drilling may beundertaken by a subsequent drill bit, without the requirement of theremoval of the earlier or first drill bit from the well bore, andwherein the earlier or first drill bit includes nozzles.

Other objects and features of this invention will become apparent fromtime to time throughout the specification and claims as hereinafterrelated.

SUMMARY OF THE INVENTION

The foregoing objectives are accomplished by a new and improved drillbit nozzle comprising a body defining a through bore, wherein thethrough bore defines a passage for drilling fluid in use, wherein thesurface of the through bore within the body has a relatively highresistance to erosion and wherein the nozzle is characterised in thatthe body is made substantially of a material or materials that allow forthe nozzle to be subsequently drilled through by standard well boredrilling equipment.

Preferably, the through bore has an enlarged concave portion at an inletside of the nozzle, communicating with a smaller diameter cylindricalportion.

The nozzle body may be made of two materials, wherein the surface of thethrough bore is made of a first material, wherein said first material isof relatively thin construction and has a high resistance to erosion,and wherein the remainder of the nozzle body is made of a secondmaterial that is easily drillable.

The first or surface material may be a hard chrome. Alternatively,tungsten carbide or suitable alloys may be used, their suitability beingassessed by their ability to withstand erosive forces from the wellfluid jetted through the through-bore.

The second material forming substantially the majority of the nozzlebody may be made typically of a softer metal, such as nickel, aluminium,copper or alloys of these.

Preferably, the second material may be copper and the surface or firstmaterial is hard chrome, wherein the hard chrome is applied to thecopper body by electro-plating.

Alternatively, a nozzle in accordance with the present invention may bemade of a rubber material. In this respect, it is noted that whilerubber is typically not a “hard” material, it does nevertheless have ahigh resistance to erosion. Moreover, rubber materials may be easilydrilled by subsequent drilling bits.

It may be seen therefore that a nozzle in accordance with invention maybe made of one or more materials and that it need not be made entirelyor even partially of a metal material. It is also envisaged, forexample, that polyurethane or other elastomers may be used.

BRIEF DESCRIPTION OF THE DRAWINGS

An example embodiment of the invention will now be described withreference to the accompanying Figures in which:

FIG. 1 a) is a sectional elevation of an earth boring drill bit nozzle;

FIG. 1 b) is a simple sectional view through the section y—y on FIG. 1a); and

FIG. 2 shows a further drill bit nozzle made substantially of anon-metallic material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring firstly to FIG. 1, there is shown a drill bit nozzle 1. Thedrill bit nozzle 1 is adapted to be threadably engaged with a drill bitbody (not shown) by virtue of the threaded portions 2. The nozzle 1 isprovided with an annular body 3 that defines a through passage orthrough bore 4.

The through bore 4 is formed with an inlet having a concave enlargedportion 4 a which communicates with a cylindrical smaller diameterportion 4 b leading to an outlet 7. The geometry of the through-bore 4is such that well fluid is jetted at high velocity out the outlet 7.

It is recognised in the invention that the nozzle through-bore 4 isintended to receive drilling fluid at high velocities and with highpressure differentials. Accordingly, the surface 5 of the through bore 4is constructed of a material that is suitable for withstanding theabrasive and eroding nature of the drilling fluid in use. Not only mustthe surface of the through passage withstand the eroding forces of thedrilling fluid, but in view of the proximity of the nozzles to thecutting surface of the drill bit, excessive wear may be induced in theevent of a nonresistant material being employed as a result of theimpact of small rock particles and other debris cut by the drill bitfrom the well formation. The erosive effect of rock particles withindrill bit nozzles is well known and documented. For this reason, thesurface of the through bore 4 is preferably made from a hard materialwhich, in an example embodiment of FIG. 1, is a hard chrome material. Inanother example, tungsten carbide may be used as the surface material.

However, the surface material will typically be chosen as one which isable to be combined with a softer drillable material whereby this softerdrillable material may form substantially the body of the drill bitnozzle, with the exception of the surface herein before mentioned. Inthe example embodiment illustrated in FIG. 1, the second material fromwhich substantially all of the nozzle body is made is copper. Copper isselected as one suitable material as the surface coating of hard chromemay be easily applied to the copper body by electro-plating means.Additionally, copper is sufficiently soft to allow a subsequent drillbit to drill through the body of the nozzle.

Turning now to FIG. 2, an alternative nozzle in accordance with thepresent invention is generally depicted at 10. The nozzle 10 is madesubstantially of a single non-metallic material, namely rubber. However,to enable the rubber nozzle to be attached to a drill bit body, thenozzle is provided with a threaded insert made of a metallic material.The threaded insert 11 is, nevertheless, made of a material which issufficiently soft to allow a subsequent drill bit to drill through it.

An advantage of the present invention will be apparent from the methodof use of the drill bit nozzle as shown in the Figures and describedabove which allows for a drill bit bearing drill bit nozzles to be leftin a well bore during the cementing of casing and subsequently drilledthrough by standard well bore drilling equipment to allow for the wellto be extended.

The invention may be seen to overcome the difficulty of providing drillbit nozzles in a manner that allowed for their resistance to wear fromthe erosive characteristics of jetted drilling fluid, while neverthelessenabling subsequent conventional or standard well bore drillingequipment to drill through them.

Further modifications and improvements may be incorporated withoutdeparting from the scope of the invention herein intended.

1. A drill bit nozzle comprising a body defining a through bore, whereinthe through bore defines a passage for drilling fluid in use, whereinthe through bore includes a surface made from a relatively hard chromehaving a relatively high resistance to erosion and wherein the nozzle ischaracterised in that the body is made substantially of one or morematerials that allow for the nozzle to be subsequently drilled throughby standard well bore drilling equipment.
 2. The drill bit nozzle ofclaim 1, wherein the through bore includes an enlarged concave portionat an inlet side of the nozzle, communicating with a smaller diametercylindrical portion.
 3. The drill bit nozzle of claim 1, wherein thebody is made of two materials, wherein a first material is the hardchrome, said first material being of relatively thin construction, andwherein the body is made of a second material that is easily drillable.4. The drill bit nozzle of claim 3, wherein the second material is asofter metal comprising nickel or aluminum or copper or alloys of these.5. A The drill bit nozzle of claim 3, wherein the second material iscopper, wherein the hard chrome is applied to the copper body byelectro-plating.
 6. The drill bit nozzle of claim 1, wherein the nozzleis made substantially by a rubber, polyurethane or other elastomers. 7.A method of drilling a well bore: (a) drilling a bore to a first depthusing a first drill bit having at least one nozzle, the nozzlecomprising a body having a bore for fluid communication through thenozzle, wherein a surface of the bore is fabricated from a relativelythin construction of chrome having a relatively high resistance toerosion; and (b) drilling the bore to a second depth using a seconddrill bit, the second depth being deeper than the first depth andcharacterised in that the second, drill bit drills through the firstdrill bit in the bore at the first depth.
 8. A drill bit nozzlecomprising a body defining a through bore for passage of drilling fluidin use, the through bore includes a surface made from a relatively thinconstruction of hard chrome having a relatively high resistance toerosion and the body is made of copper that allows the nozzle to besubsequently drilled through by standard well bore drilling equipment,wherein the hard chrome is applied to the copper body byelectro-plating.
 9. A nozzle for use with a drill bit comprising a bodyhaving a bore for fluid communication through the nozzle, wherein asurface of the bore is fabricated from a relatively thin construction ofchrome having a relatively high resistance to erosion.
 10. The nozzle ofclaim 9, wherein the hard chrome is applied to the body byelectro-plating.
 11. A nozzle for use with a drill bit comprising: abody made substantially from copper, the body having a bore for fluidcommunication through the nozzle, a surface of the bore is made from arelatively thin material having a relatively high resistance to erosion.12. The nozzle of claim 11, wherein the thin material is hard chrome.13. The nozzle of claim 11, wherein the thin material is a tungstencarbide or suitable alloy.